Magnetic pick up with fluxbridge and replaceable stylus

ABSTRACT

A stereophonic magnetic tone pickup with an armature, which distributes the magnetic flux corresponding with the needle position differently over four magnetic, parallel disposed paths. Two oppositely disposed paths are connected by a magnetic bridge, which contains a spool. A different magnetic flux in the four parallel paths leads to an equalization flux over the bridge, which flux induces in turn the use voltage.

United States Patent 1 Laue [ Sept. 18, 1973 1 1 MAGNETIC PICK UP WITH FLUXBRIDGE AND REPLACEABLE STYLUS [75] Inventor: Eckhard Laue, St. Georgen,

Schwarzwald, Germany [73] Assignee: Dual Gerbrueder Steidlnger,

Georgen/Schwarzwald, Germany 221 Filed: Mar. 31, 1972 211 App]. No.: 240,879

[52] U.S. Cl... 179/l00.4l K, 179/100.4] Z, 274/37 [51] Int. Cl I-I04r 11/12 [58] Field oiSearch 179/1004] K, 100.41 Z;

[56] References Cited UNITED STATES PATENTS ll/l962 Pritchard 119/10041 K ll/l965 Dally 274m 3,220,738 11/1965 Dally 274/37 3,469,040 9/1969 Shaper..... 179/1004] K 3,614,332 10/1971 Nagasaki 179/1004] K FOREIGN PATENTS OR APPLICATIONS 257,496 10/1964 Australia 179/1004] K Primary Examiner-Raymond F. Cardillo, Jr. Attorney-Ernest G. Montague [57] ABSTRACT A stereophonic magnetic tone pickup with an armature, which distributes the magnetic flux corresponding with the needle position differently over four magnetic, parallel disposed paths. Two oppositely disposed paths are connected by a magnetic bridge, which contains a spool. A difierent magnetic flux in the four parallel paths leads to an equalization" flux over the bridge, which flux induces in turn the use voltage. v

4 Claims, 3 Drawing Figures MAGNETIC PICK UP WITH FLUXBRIDGE AND REPLACEABLE STYLUS The present invention relates to a magnetic tone pickup for the reproduction of a sound groove modulated in two directions disposed perpendicularly towards each other with a rod-shaped armature needleunit, the needle carrier of which carries at one end a sensing point and at the other end a magnet armature which is retained in an elastic bearing swingable towards all sides such, that the one end of the anchor armature is disposed in the center of four ends of pole pieces disposed symmetrically about the center at a short distance, which pole pieces are in connection at the other end with intermediate arrangement of an air gap with one pole of a joint, permanent magnet, the counter pole of which is in connection as a joint fifth pole with the other armature end. As a consequence of a position variation of the armature relative to the pole ends, the magnetic flux distribution onto the pole pieces varies and thereby in an electric winding, which is coordinated each to a pair of oppositely disposed pole pieces, and a tension voltage is induced.

in tone pickups of the above described type, there is a core of a spool each of the four pole pieces and two oppositely disposed spools are joined in series to an electric winding. The advantage of such arrangement resides in the fact of a non-symmetric position of the armature to the pole end, which leads to a different induction in the spools, is equalized by the series arrangement of the spools. The four spools necessary thereby constitute non-neglectable expenditure. Other tone pickups with only two variable air gaps or magnetic circuits, respectively, each with only one spool, and of a lesser expenditure, do not have, however, the equalization effect.

It is one object of the present invention to provide a magnetic tone pickup having this equalization effect, which is, however, simple in its structure.

It is another object of the present invention to provide a magnetic tone pickup, wherein two oppositely disposed pole pieces are connected by a magnetic, conducting'bridge and each bridge carries an electric winding. In accordance with this arrangement, it is possible, while obtaining the same effect, to find only two spools sufficient.

Tone pickups with an anchor swinging between four poles are, as a rule, designed such, that the mounting unit necessary for the needle change comprises the armatureneedle-unit, the elastic bearing or support and a small tube surrounding the other elements, which small tube is insertable between the four poles. The small tube is thereby necessary for a safe manipulation during the needle exchange and the maintenance of the mechanical characteristics in case of a needle change. Yet, to a small air gap and, thereby, to a sufficient sensitivity, certain limits are set, in case of a small inner impedance. This applies to the four operating air gaps, as well as to the air gap at the fifth pole. A tone pickup is known, though, the armature-needle-unit of which is provided in a small tube, which is rigidly embedded, on the one hand, in a mounting unit serving the needle change, which mounting unit contains simultaneously also pole pieces. This mounting unit is pressed by means of screws against connection-pole pieces disposed in the tone pickup. Such arrangement is, however, expensive, since once two connectable pole pieces are required for the magnetic circular part from the armature to the spools and, on the other hand, additional securing means for the mounting unit, which brings about also a complicated manipulation.

It is yet another object of the present invention, to provide a magnetic tone pickup which makes possible small air gaps at the armature with a simplified structure, without endangering the maintenance during a needle change by the layman. It is based on the recognition, that an improvement is possible only by means of smaller air gaps, that means, without intermediate parts and in the interest of a low magnetic impedance all these parts are to be joined to one structural unit, between which a movement is necessary and for which, due to small flux densities, small dimensions are of advantage, as the armature, the four and,-first of all, also the fifth joint pole and, therefore, the separating points are to be engaged with larger faced robust parts, whereby also a particular analogous manipulation is to be attempted.

It is still another object of the present invention to provide a magnetic pickup wherein the armatureneedle-unit together with the fourpole ends are disposed in pairs opposite each other and the fifth pole end constitutes a structural unit capable of being plugged to the pickup, whereby .the pole pieces disposed oppositely each other in pairs are formed as plugs at their end remote from the armature which, upon connection with the pickup form the complete four line magnetic path..

The armature for the pickups of the above stated type is, as a rule, a prismatic body, which, during swinging about a point of its longitudinal axis, comes closer with its end to one of the ends of the pole pieces. For the practical manipulation of the pickup, a much larger swinging angle of the armature is required, as it corresponds with the modulation of the sound groove, which means, the air gap must be appreciably larger than it is required by the transmitter function. A smaller air gap results, however, in the smaller magnetic impedance and thereby a greater sensitivity or a lower inner impedance of the pickup also, which both are of essential advantage.

In accordance with a further development of the present invention, the impedance of the magnetic circuit is to be reduced, without narrowing the swinging range of the armature.

It is also a further object of the present invention to provide a magnetic tone pickup wherein the outer face of the armature has the form of a spherical cap, the rotary point during swinging of the armature-needle-unit is disposed at a semi center of the ball and the faces of all pole ends are arranged substantially parallel to the outer face of the anchor such, that during swinging of the armature needle unit the overlapping measure a of the oppositely disposed faces of the armature varies,

and in pairs the oppositely disposed ends of the polev pieces vary. In accordance with this arrangement, the control between the swinging arrangement of the armature and the size of the air gap is eliminated.

With these and other objects in view, which will become apparent in the following detailed description, the present invention, which is shown by example only, will be clearly understood in connection with the accompanying drawings, in which FIG. 1 is a longitudinal section of a magnetic tone pickup and in particular, along the lines I-I of FIG. 2;

FIG. 2 is a section along the lines II-II of FIG. 1; and

FIG. 3 is a section of an exchangeable mounting unit with the armature-needle-unit shown at an enlarged scale.

Referring now to the drawings, the pickup in accordance with the present invention comprises substantially a permanent magnet 1, a front and a rear yoke sheet 2 and 3, four magnetically conducting pole pieces 4 to 7, which are connected in pairs each by a magnetically conducting bridges 8 and 9, each of which carries a spool 10 and 11, Between the pole ends 12 and 13 of the pole pieces 4 and 5 and the front yoke sheet 2 is disposed an armature 14, which forms a single unit with a needle carrier 15 with a sensing point 16. Each pole piece 4 to 7 is a part of a particular parallel disposed magnetic flux circuit, the impedance of which is varied by a swinging of the anchor 14 about its rotary point 17, as will be more clearly disclosed below, and, in particular, an increase in one pole piece corresponds to a decrease in the oppositely disposed pole piece. The

' magnetic impedance of the pole pieces 4 to 7 and of the bridges 8 and 9 is very small in relation to the air gaps, that is, thus on both ends of the bridges 8 and 9. Since only the magnetic impedance in the pole piece sections of the bridge ends up to the rear yoke sheet 3 is equally large, in these pole piece sections always an equally larger flux must flow, that is, if in the afore-mentioned pole piece sections as a consequence of an unsymmetrical position of the armature, the magnetic fluxes are differently large, consequently equalizing these differences over the bridges 8 and 9, that is whether the anchor is exactly symmetrically arranged or not.

All parts between which a movement is necessary and for which, due to low flux cross sections, small dimensions are of advantage, and are combined in the mounting unit in FIG. 3. The front yoke sheet 2 is rigidly connected with the pole pieces 4 to 7 by means of a body 22 of synthetic material. The projecting ends of the pole pieces are formed as plugs and insertable into corresponding recesses on the tone pickup, whereby a geometrically exact and reliable connection with the yoke sheet 3 and the bridges 8 and 9 is brought about. This arrangement permits the use of spools 10 and 11 without spool bodies, without inviting the danger thereby, that the spools could be damaged by insertion of the pole pieces. The front yoke sheet 2 forms a fifth pole l8 and, simultaneously, a screen for the four operating air gaps on the armature and makes possible thereby a joint-less connection of the spool screen 23,

which extends up to short of the rear yoke sheet 3. A certain distance is required, in order to avoid a short circuit.

At the end of the tubular needle carrier 15 a semi ball-shaped anchor 14 and a thread 24 of synthetic material are secured.

By means of the thread of synthetic material 24, the armature 14 is pulled via an intermediate arrangement of a rubber disk 25 against a disk 26, the latter sitting rigidly in the body 22 of the synthetic material. The dimensions are chosen such, that the point 17, about which an armature needle unit is swingable, coincides with the substantially semi center point of the ball, which forms partly the armature surface, so that the width of the air gap 17" is not changed if the armature 6 pivots. The air gap b" can be maintained very small thereby. The surface of the armature 14 is overlapped by the pole ends 12 and 13 in the range of the measure a. During swinging of the armature 14 about its rotary point 17, this overlapping measure a varies and thereby the magnetic impedance, while it remains constant between the armature l4 and the joint fifth pole 18.

While I have disclosed one embodiment of the present invention, it is to be understood that this embodiment is given by example only and not in a limiting sense.

I claim:

1. A pick up comprising a magnetic flux-conducting armature,

a rod-shaped needle-holder disposed coaxially to said armature and connected with the latter,

a sensing needle secured to a free end of said needleholder and together with said armature constituting an armature-needle unit,

an elastic support means for holding said armatureneedle unit swingable about a longitudinal axis in a carrying body,

four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and arranged to form two pairs of oppositely disposed pole pieces and such that one end of each of said four magnetic pole pieces being disposed concentrically to said armature therebehind and slightly adjacently spaced therefrom, said pole pieces haivng free ends remote from said armature,

a magnetically flux-conducting return path means being adjacent said armature and slightly spaced therefrom,

a permanent magnet operatively arranged between said return path means and said free ends of said pole pieces, and stationarily disposed, a magnetically flux-conducting bridge disposed between each of said pair of oppositely disposed pole pieces, and

an electric winding on each of said two bridges.

2. The mounting unit, as set forth in claim 1, wherein said path means is formed with an opening, through which extends said armature-needle unit and which encloses in a pot-shape said armature as well as said one ends of said four pole pieces.

3. A mounting unit attachable to a magnetic pick up,

comprising a carrying body defining a longitudinal axis,

a magnetically flux conducting armature,

a rod-shaped needle holder connected coaxially with said anchor,

a sensing needle secured to a free end of said needle holder and constituting together with said armature an armature-needle unit,

an elastic support means for holding said armatureneedle unit swingable about said longitudinal axis in said carrying body,

four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and disposed to form two pairs of oppositely disposed pole pieces and such that one end of each of said four pole pieces being arranged concentrically to said armature and adjacent and slightly spaced therefrom, said pole pieces having free ends remote from said armature,

said free ends, remote from said anchor of said pole pieces being formed as four parallel disposed pins adapted to form a complete four-line path upon plugging to a pickup, and

a magnetically flux-conducting path means secured to said carrying body and being adjacent said armature and slightly spaced therefrom and constituting a fifth pole opposite to said one ends of said four pole pieces,

a magnetic flux-conducting bridge disposed between each of said pairs of oppositely disposed pole pieces, and

an electrical winding on each of said bridges.

4. A mounting unit connectable with a magnetic pickup, comprising a carrying body defining a longitudinal axis,

a substantially semi-ball-shaped, magnetically fluxconducting armature,

a rod-shaped needle holder connected coaxially with said armature and projecting on the side of said ball and constituting together with said armature an armature-needle unit,

an elastic support means for holding said armature needle unit swingable in said carrying body about a point on said longitudinal axis, which point constitutes the center point of said semi-ball, and

four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and arranged to form two pairs of oppositely disposed pole pieces and such that one end of each of said four pole pieces being disposed slightly spaced from and concentrically to said semi-ball armature and said one ends of said pole pieces overlap said semi-ball arranged by a predetermined measure, the latter being larger than its radial distance from said semi-ball armature;

a magnetic flux conducting bridge disposed between each of said pairs of oppositely disposed pole pieces, and

an electrical winding on each of said bridges. 

1. A pick up comprising a magnetic flux-conducting armature, a rod-shaped needle-holder disposed coaxially to said armAture and connected with the latter, a sensing needle secured to a free end of said needle-holder and together with said armature constituting an armature-needle unit, an elastic support means for holding said armature-needle unit swingable about a longitudinal axis in a carrying body, four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and arranged to form two pairs of oppositely disposed pole pieces and such that one end of each of said four magnetic pole pieces being disposed concentrically to said armature therebehind and slightly adjacently spaced therefrom, said pole pieces haivng free ends remote from said armature, a magnetically flux-conducting return path means being adjacent said armature and slightly spaced therefrom, a permanent magnet operatively arranged between said return path means and said free ends of said pole pieces, and stationarily disposed, a magnetically flux-conducting bridge disposed between each of said pair of oppositely disposed pole pieces, and an electric winding on each of said two bridges.
 2. The mounting unit, as set forth in claim 1, wherein said path means is formed with an opening, through which extends said armature-needle unit and which encloses in a pot-shape said armature as well as said one ends of said four pole pieces.
 3. A mounting unit attachable to a magnetic pick up, comprising a carrying body defining a longitudinal axis, a magnetically flux-conducting armature, a rod-shaped needle holder connected coaxially with said anchor, a sensing needle secured to a free end of said needle holder and constituting together with said armature an armature-needle unit, an elastic support means for holding said armature-needle unit swingable about said longitudinal axis in said carrying body, four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and disposed to form two pairs of oppositely disposed pole pieces and such that one end of each of said four pole pieces being arranged concentrically to said armature and adjacent and slightly spaced therefrom, said pole pieces having free ends remote from said armature, said free ends, remote from said anchor of said pole pieces being formed as four parallel disposed pins adapted to form a complete four-line path upon plugging to a pickup, and a magnetically flux-conducting path means secured to said carrying body and being adjacent said armature and slightly spaced therefrom and constituting a fifth pole opposite to said one ends of said four pole pieces, a magnetic flux-conducting bridge disposed between each of said pairs of oppositely disposed pole pieces, and an electrical winding on each of said bridges.
 4. A mounting unit connectable with a magnetic pickup, comprising a carrying body defining a longitudinal axis, a substantially semi-ball-shaped, magnetically flux-conducting armature, a rod-shaped needle holder connected coaxially with said armature and projecting on the side of said ball and constituting together with said armature an armature-needle unit, an elastic support means for holding said armature-needle unit swingable in said carrying body about a point on said longitudinal axis, which point constitutes the center point of said semi-ball, and four magnetic flux-conductable parallel disposed pole pieces secured in said carrying body and arranged to form two pairs of oppositely disposed pole pieces and such that one end of each of said four pole pieces being disposed slightly spaced from and concentrically to said semi-ball armature and said one ends of said pole pieces overlap said semi-ball arranged by a predetermined measure, the latter being larger than its radial distance from said semi-ball armature; a magnetic flux conducting bridge disposed between each of said pairs of oppositely disposed pole pieces, and an electrical winding on each of said bridges. 